Tackified And Non-Tackified Nonwovens Of Controlled Stiffness And Retained Foldability

Abstract

The present disclosure relates generally to a nonwoven filtration media comprising a bonded mix of different, discontinuous, thermoplastic resin fibers and optionally discontinuous cellulosic fibers. In some embodiments a tackifier is added to the nonwoven filtration media to provide a sticky or adhesive surface on the fibers. The nonwoven media has an advantageous combination of stiffness, foldability, efficiency and the ability to retain a fold. The nonwoven media can be thermally bonded during the production process. The advantageous combination of mechanical properties allow the disclosed nonwoven media to accept and retain folds and pleats better than some conventional filtration materials while the mix of different fibers provides desirable filtration properties.

1 . A tackified air filtration media comprising a thermally bonded nonwoven web comprising a generally homogeneous mixture of fiber types, the web comprising about 10% to about 90% by weight of a first type of fibers having a length of about 0.6 cm to about 20 cm, the fibers including a first fiber portion extending substantially continuously along the length of each fiber and comprising a first thermoplastic polymeric material having a first melting point and a second fiber portion extending substantially continuously along the length of each fiber and defining at least a portion of a fiber exterior surface, the second fiber portion comprising a second thermoplastic polymeric material having a second melting point lower than the first melting point, and about 10% to about 90% by weight of a second type of fibers having a length of about 0.6 cm to about 20 cm; the media having a basis weight in the range of about 90 gsm to about 370 gsm; a thickness of about 1.0 mm to about 6.4 mm; a Frazier permeability of about 150 CFM/square foot to about 1000 CFM/square foot; and a combination of MD Gurley stiffness and LED score results selected from one of the following ranges: 
       
         
           
                 
                 
                 
               
                     
                 
                   range 
                   Gurley Stiffness (mg) 
                   LED score (degrees) 
                 
                     
                 
                   A 
                   Over 3000 
                   60.2 to 101.7 
                 
                   B 
                   2800 to 3000 
                   55.0 to 104.2 
                 
                   C 
                   2400 to 2800 
                   53.3 to 101.5 
                 
                   D 
                   1800 to 2400 
                   39.7 to 108.2 
                 
                   E 
                   1400 to 1800 
                   41.2 to 98.3  
                 
                   F 
                   1200 to 1400 
                   77.0 to 86.0  
                 
                   G 
                    800 to 1200 
                   39.3 to 68.2  
                 
                   H 
                   Under 800 
                   42.7 to 68.8  
                 
                     
                 
             
                
                
                
               
               
                
                
                
                
                
                
                
                
                
               
            
           
         
       
       and;
 0.5 percent by weight of nonwoven web to about 30 percent by weight of nonwoven web of a tackifier on fibers of the air filtration media. 
 
     
     
         2 . The tackified air filtration media of  claim 1 , wherein the first thermoplastic polymeric material is polyester. 
     
     
         3 . The tackified air filtration media of  claim 1  being a single layer. 
     
     
         4 . The tackified air filtration media of  claim 1 , wherein the first thermoplastic polymeric material is polyester and the second thermoplastic polymeric material is polyester. 
     
     
         5 . The tackified air filtration media of  claim 1 , further comprising kenaf fibers having a length of about 0.6 cm to about 20 cm. 
     
     
         6 . The tackified air filtration media of  claim 1 , comprising about 1.5% to about 15% of the tackifier on fibers of the air filtration media. 
     
     
         7 . The tackified air filtration media of  claim 1 , wherein one fiber type has a denier in the range of about 0.9 to about 6 and the other fiber type has a denier in the range of about 8 to about 45. 
     
     
         8 . The tackified air filtration media of  claim 1 , further being a self supporting media. 
     
     
         9 . The tackified air filtration media of  claim 1 , having a MD Gurley stiffness over 1700. 
     
     
         10 . The tackified air filtration media of  claim 1 , wherein:
 the first fiber type is selected from at least one of about 10% to about 85% 4 denier conjugate fibers comprising polyester first and second fiber portions or about 10% to about 85% 15 denier conjugate fibers comprising polyester first and second fiber portions;   the second fiber type is selected from at least one of about 5% to about 30% monocomponent polyester fibers having a denier in the range of about 0.9 to about 45; about 15% to about 50% 3 denier chargeable polypropylene fibers; about 15% to about 30% polyester/cotton blend fibers; or about 15% to about 35% cellulosic fibers;   at least one fiber type has a denier greater than 10; and   about 1.5% to about 6% tackifier.   
     
     
         11 . The tackified air filtration media of  claim 1  further comprising a cured, non-fibrous binder resin between the fiber types. 
     
     
         12 . The tackified air filtration media of  claim 1  having a combination of Gurley stiffness and LED score results selected from one of the following ranges: 
       
         
           
                 
                 
                 
               
                     
                 
                   range 
                   Gurley Stiffness (mg) 
                   LED score (degrees) 
                 
                     
                 
                   A 
                   over 3,000 
                   60.2 to 85.8; 
                 
                   B 
                   2,800 to 3,000 
                   60.2 to 90.8; 
                 
                   C 
                   2,400 to 2,800 
                   58.2 to 79.0; 
                 
                   D 
                   1,800 to 2,400 
                   40.0 to 94.7; 
                 
                   E 
                   1,400 to 1,800 
                   42.5 to 94.0; 
                 
                   F 
                   1,200 to 1,400 
                   43.3 to 64.8; 
                 
                   G 
                     800 to 1,200 
                   39.3 to 63.3; 
                 
                   H 
                   under 800 
                   42.7 to 68.8. 
                 
                     
                 
             
                
                
                
               
               
                
                
                
                
                
                
                
                
                
               
            
           
         
       
     
     
         13 . A method of making a tackified air filtration media comprising:
 forming a fiber mixture, comprising about 10% to about 90% by weight of a first type of fibers having a length of about 0.6 cm to about 20 cm, the fibers including a first fiber portion extending substantially continuously along the length of each fiber and comprising a first thermoplastic polymeric material having a first melting point and a second fiber portion extending substantially continuously along the length of each fiber and defining at least a portion of a fiber exterior surface, the second fiber portion comprising a second thermoplastic polymeric material having a second melting point lower than the first melting point, and about 10% to about 90% by weight of a second type of fibers having a length of about 0.6 cm to about 20 cm;   forming the fiber mixture into a nonwoven matt;   bonding the fibers in the nonwoven matt, the bonded nonwoven matt having a basis weight in the range of about 90 gsm to about 370 gsm; a thickness of about 1.0 mm to about 6.4 mm; a Frazier permeability of about 150 CFM/square foot to about 1000 CFM/square foot; and a combination of MD Gurley stiffness and LED score results selected from one of the following ranges:   
       
         
           
                 
                 
                 
               
                     
                 
                   range 
                   Gurley Stiffness (mg) 
                   LED score (degrees) 
                 
                     
                 
                   A 
                   Over 3000 
                   60.2 to 101.7 
                 
                   B 
                   2800 to 3000 
                   60.2 to 104.2 
                 
                   C 
                   2400 to 2800 
                   53.3 to 101.5 
                 
                   D 
                   1800 to 2400 
                   39.7 to 105.3 
                 
                   E 
                   1400 to 1800 
                   41.2 to 94.5  
                 
                   F 
                   1200 to 1400 
                   42.0 to 86.0  
                 
                   G 
                    800 to 1200 
                   39.3 to 68.2  
                 
                   H 
                   Under 800 
                   42.7 to 68.8  
                 
                     
                 
             
                
                
                
               
               
                
                
                
                
                
                
                
                
                
               
            
           
         
       
       and;
 applying 0.5 percent by weight of nonwoven web to about 30 percent by weight of nonwoven matt of a tackifier to fibers of the bonded nonwoven matt to form the tackified air filtration media. 
 
     
     
         14 . The method of  claim 13  wherein the step of forming comprises carding the fiber mixture to form the nonwoven matt. 
     
     
         15 . The method of  claim 13  wherein the step of forming comprises carding the fiber mixture to form a web and cross lapping the web to form the nonwoven matt. 
     
     
         16 . The method of  claim 13  wherein the step of bonding comprises thermal bonding of the fibers in the nonwoven matt. 
     
     
         17 . The method of  claim 13  wherein the step of applying comprises spraying a tackifier on a surface of the bonded nonwoven matt. 
     
     
         18 . The method of  claim 13  further comprising the step of folding the media to form a self supporting structure. 
     
     
         19 . A non-tackified air filtration media comprising a thermally bonded nonwoven web comprising a generally homogeneous mixture of fiber types, the web comprising about 30% to about 90% by weight of a first type of fibers having a length of about 0.6 cm to about 20 cm, the fibers including a first fiber portion extending substantially continuously along the length of each fiber and comprising a first thermoplastic polymeric material having a first melting point and a second fiber portion extending substantially continuously along the length of each fiber and defining at least a portion of a fiber exterior surface, the second fiber portion comprising a second thermoplastic polymeric material having a second melting point lower than the first melting point, and about 5% to about 70% by weight of a second type of fibers having a length of about 0.6 cm to about 20 cm; the media having a basis weight in the range of about 90 gsm to about 370 gsm; a thickness of about 1.0 mm to about 6.4 mm; a Frazier permeability of about 45,000 LSM to about 260,000 LSM; and a combination of Gurley stiffness and LED score results selected from one of the following ranges: 
       
         
           
                 
                 
                 
               
                     
                 
                   range 
                   Gurley Stiffness (mg) 
                   LED score (degrees) 
                 
                     
                 
                   A 
                   Over 3000 
                   60.2 to 101.7 
                 
                   B 
                   2800 to 3000 
                   60.2 to 104.2 
                 
                   C 
                   2400 to 2800 
                   53.3 to 101.5 
                 
                   D 
                   1800 to 2400 
                   39.7 to 105.3 
                 
                   E 
                   1400 to 1800 
                   41.2 to 94.5  
                 
                   F 
                   1200 to 1400 
                   42.0 to 86.0  
                 
                   G 
                    800 to 1200 
                   39.3 to 68.2  
                 
                   H 
                   Under 800 
                   42.7 to 68.8  
                 
                     
                 
             
                
                
                
               
               
                
                
                
                
                
                
                
                
                
               
            
           
         
       
     
     
         20 . The non-tackified air filtration media of  claim 19 , wherein one fiber type has a denier less than about 6 and the other fiber type has a denier greater than about 8.